I was the one who said it was a 5 hour drive. It might be more for her. She lives North of me, and I don't remember how far South she is going. I do not agree, with letting her horse out, at a rest stop. It's a holiday weekend, and the roads and rest stops will be jammed. If he got scared and got away from them. It could turn into a real mess. She could, and should stop and let him rest, while in the trailer. Ours would pee in the trailer, but didn't want water. We always kept a hay bag in front of them also.
Yeah, I thought about that, but I've done it before. I just make sure I park in an area where there are no cars. But you're right, on their "Maiden Voyage" they're probably safer just leaving him in the trailer. They could stop for a lunch break and offer him some water then. That would give him time to relax for a while. Keeping their balance in a moving trailer takes a lot out of a horse.